The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Referring now to FIG. 1, a hard disk drive (HDD) 10 includes a hard disk assembly (HDA) 12 and a HDD printed circuit board (PCB) 14. PCB 14 provides mounting points and electrical connections for various modules of HDD 10 that are described herein. HDA 12 includes one or more platters 16 that are coated with magnetic material for storing data. Platters 16 are arranged in a concentric stack that is rotated by a spindle motor 18. Read/write heads 20 read and write data to and from corresponding surfaces of platters 16. Heads 20 are mounted at ends of corresponding actuator arms 22. A voice coil motor (VCM) 24 moves actuator arms 22 to position heads 20 over desired data tracks on platters 16.
A preamplifier module 26 amplifies signals from heads 20 and communicates the amplified signals to a read/write channel module 28. Read/write channel module 28 performs analog-to-digital (A2D) and digital-to-analog (D2A) conversions on the data that is communicated with HDA 12.
Platters 16 include servo data that is written on platters 16 at predetermined locations and provide reference points for locating the data tracks on platters 16. In some implementations a self-servo write (SSW) module 42 generates the servo data before data can be stored on platters 16.
A hard drive control (HDC) module 30 controls operation of HDD 10. For example, HDC module 30 generates commands that control the rotational speed of spindle motor 18 and the position of arms 22 over selected tracks of platters 16. Based on the commands, a spindle/VCM driver module 34 generates control signals that control the speed of spindle motor 18 and the positions of VCM 24 and actuator arms 22.
HDC module 30 communicates the data stored in HDA 12 with an external device (not shown) via an interface 40. Examples of external devices include computers, televisions, set top boxes, digital video recorders, personal digital assistants, cellular phones, media or MP3 players, and the like. Interface 40 may include a wired and/or a wireless communication link that is compatible with wireless local area network (WLAN), Ethernet, advanced technology attachment (ATA), serial ATA (SATA), integrated drive electronics (IDE), enhanced IDE (EIDE), small computer system interface (SCSI), Peripheral Component Microchannel Interconnect Architecture (PCMCIA), peripheral component interconnect (PCI), extended PCI (PCIx), enhanced PCI (PCIe), and the like.
A processor 32 processes the data to implement functions such as data encoding, decoding, filtering, and/or formatting and the like. Processor 32 may also process the servo data to facilitate positioning heads 20 over a selected one of the data tracks on platters 16.
HDC module 30 can use volatile memory 36 and/or flash memory 38 to cache data that passes through interface 40. Volatile memory 36 may include dynamic random access memory (DRAM), synchronous DRAM (SDRAM), Rambus (DRAM), static RAM, and the like. Flash memory 38 has a finite life span and can render HDD 10 inoperative when non-volatile memory 38 reaches its end-of-service life. In some embodiments flash memory 38 has a life span of about 1×105 or 1×106 write cycles.
Using flash memory 38 to cache data waiting to be written to HDA 12 or read by interface 40 has a number of possible benefits. These benefits include faster access time, higher transfer rate, power savings, quicker resumption from a hibernate state, and greater reliability. Data read from HDA 12 or not yet written to HDA 12 can be accessed more quickly from flash memory 38 than from HDA 12.
Further, data can be accessed from flash memory 38 without having to power HDA 12 and spin platters 16. HDA 12 may then only require power intermittently to provide read data to flash memory 38 and flush write data from nonvolatile memory 38. While platters 16 are not rotating, HDA 12 is much less prone to physical damage, such as from drops or sudden impacts.